Add Docs for chromeexts

BUG=1168231

Change-Id: I53576e90421502a90522f71c0bcd2b027006de60
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2725316
Auto-Submit: Robert Liao <robliao@chromium.org>
Commit-Queue: Wei Li <weili@chromium.org>
Reviewed-by: Wei Li <weili@chromium.org>
Cr-Commit-Position: refs/heads/master@{#858609}

tools/win/chromeexts/README.md

@@ -0,0 +1,83 @@
+# chromeexts - Chrome's Windbg Extension
+
+`chromeexts` is a debugger extension that works in `cdb`, `ntsd`, and `windbg`.
+
+[TOC]
+
+## Loading chromeexts
+
+First build the `chromeexts` build target with `ninja` and then in the debugger,
+run the following command:
+
+```
+> .load [Path to the chromeexts.dll]
+```
+
+After that, the following commands will work in the debugger.
+
+## UI Commands
+
+### !view
+
+```
+> !views [options] <Address To View Object>
+```
+
+Provides information about a `view` object in a easy to read format.
+
+| Option      | Description |
+|:-----------:|-------------|
+| `/children` | Output the addresses of all children |
+| `/r`        | Requires `/children`. Output all children recursively. |
+
+#### Examples
+
+Simple Output
+
+```
+> !view 0x250a57f0
+Bounds: 0,9 (1042x1077)
+Parent: 0x250801a8
+```
+
+Viewing the Children
+
+```
+> !view /children 0x250a57f0
+Child Count: 4
+25b9e368 25b91110 2507e0a8 2507fd78
+```
+
+Viewing the Children Recursively
+
+```
+> !view /children /r 0x25ee8098
+Child Count: 4
+<views!views::MdTextButton::`vftable' address="0x25ee8098" bounds="274 8 32x106" enabled="false" id="0" needs-layout="false" visible="true">
+  <views!views::FocusRing::`vftable' address="0x25e2f328" bounds="-1 -1 34x108" enabled="false" id="0" needs-layout="false" visible="false" />
+  <views!views::InkDropContainerView::`vftable' address="0x25e2b9d8" bounds="0 0 32x106" enabled="false" id="0" needs-layout="false" visible="false" />
+  <views!views::ImageView::`vftable' address="0x25e2d4f8" bounds="16 16 0x0" enabled="false" id="0" needs-layout="false" visible="true" />
+  <views!views::internal::LabelButtonLabel::`vftable' address="0x25f75690" bounds="16 0 32x74" enabled="false" id="0" needs-layout="false" visible="true" />
+</views!views::MdTextButton::`vftable'>
+```
+
+### !hwnd
+
+```
+> !hwnd <Window Handle>
+```
+
+**Requires live debugger.** Provides information about an `HWND`.
+
+#### Example
+
+```
+> !hwnd 008F0638
+Title: chromeexts - Chrome's Windbg Extension - Google Chrome
+Class: Chrome_WidgetWin_1
+Hierarchy:
+   Owner: 00000000 Parent: 00000000
+   Prev:  000900c8 Next:   000402f4
+Styles: 16cf0000 (Ex: 00000100)
+Bounds: (253, 246) 1718x816
+```